yading@10: /*
yading@10:  * H261 parser
yading@10:  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
yading@10:  * Copyright (c) 2004 Maarten Daniels
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file
yading@10:  * h261codec.
yading@10:  */
yading@10: 
yading@10: #include "parser.h"
yading@10: 
yading@10: static int h261_find_frame_end(ParseContext *pc, AVCodecContext *avctx,
yading@10:                                const uint8_t *buf, int buf_size)
yading@10: {
yading@10:     int vop_found, i, j;
yading@10:     uint32_t state;
yading@10: 
yading@10:     vop_found = pc->frame_start_found;
yading@10:     state     = pc->state;
yading@10: 
yading@10:     for (i = 0; i < buf_size && !vop_found; i++) {
yading@10:         state = (state << 8) | buf[i];
yading@10:         for (j = 0; j < 8; j++) {
yading@10:             if (((state >> j) & 0xFFFFF0) == 0x000100) {
yading@10:                 vop_found = 1;
yading@10:                 break;
yading@10:             }
yading@10:         }
yading@10:     }
yading@10:     if (vop_found) {
yading@10:         for (; i < buf_size; i++) {
yading@10:             state = (state << 8) | buf[i];
yading@10:             for (j = 0; j < 8; j++) {
yading@10:                 if (((state >> j) & 0xFFFFF0) == 0x000100) {
yading@10:                     pc->frame_start_found = 0;
yading@10:                     pc->state             = (state >> (3 * 8)) + 0xFF00;
yading@10:                     return i - 2;
yading@10:                 }
yading@10:             }
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     pc->frame_start_found = vop_found;
yading@10:     pc->state             = state;
yading@10:     return END_NOT_FOUND;
yading@10: }
yading@10: 
yading@10: static int h261_parse(AVCodecParserContext *s,
yading@10:                       AVCodecContext *avctx,
yading@10:                       const uint8_t **poutbuf, int *poutbuf_size,
yading@10:                       const uint8_t *buf, int buf_size)
yading@10: {
yading@10:     ParseContext *pc = s->priv_data;
yading@10:     int next;
yading@10: 
yading@10:     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
yading@10:         next = buf_size;
yading@10:     } else {
yading@10:         next = h261_find_frame_end(pc, avctx, buf, buf_size);
yading@10:         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
yading@10:             *poutbuf      = NULL;
yading@10:             *poutbuf_size = 0;
yading@10:             return buf_size;
yading@10:         }
yading@10:     }
yading@10:     *poutbuf      = buf;
yading@10:     *poutbuf_size = buf_size;
yading@10:     return next;
yading@10: }
yading@10: 
yading@10: AVCodecParser ff_h261_parser = {
yading@10:     .codec_ids      = { AV_CODEC_ID_H261 },
yading@10:     .priv_data_size = sizeof(ParseContext),
yading@10:     .parser_parse   = h261_parse,
yading@10:     .parser_close   = ff_parse_close,
yading@10: };